Adaptec 133U2 - AAA RAID Controller User Manual page 139

The array management software and firmware support RAID 0,
RAID 1, RAID 0/1, and RAID 5 arrays. The advantages,
disadvantages, and requirements of these RAID levels are as
follows:
RAID 0 Arrays
Maximum Disks Allowed: 16
Minimum Disks Allowed: 1
In a RAID 0 array, data is distributed, or striped, across the disks in
the array. The capacity of the array is approximately equal to the
combined capacity of the physical disks. The I/O performance of a
RAID 0 array is much better than that of a single physical disk
because multiple reads and writes can be handled in parallel and
because when large files are accessed the striped data is retrieved
simultaneously from several disks.
RAID 0 arrays do not store redundant data and therefore are not
true RAID applications. If one disk fails, the entire array fails and all
data is lost. This means that the fault tolerance of a RAID 0 array is
less than that of any single disk in the array. The term RAID 0 is
widely used for these arrays, however, because they are
conceptually similar to true RAID applications.
RAID 1 Arrays
Maximum Disks Allowed: 2
Minimum Disks Allowed: 2
RAID 1 arrays use a single pair of disks. They are called mirrored
arrays because both disks in the pair contain the same data. When
data is written to a RAID 1 array it is written to each disk in the pair.
The read performance of a RAID 1 array can be much better than
that of a single disk, while the write performance is slightly worse.
Mirrored arrays are highly reliable because the data is still safe if one
disk in the pair fails. They are more costly, however, because you get
only one disk of actual storage capacity from the pair of disks.
1
If the system has a single SCSI channel, the maximum would be 15 disks
since no more than 15 drives could be installed in the system.
2
One-disk RAID 0 arrays are used only to control the virtual device order of
single disks.
Managing Arrays and Spares
1
(or as allowed by your controller)
2
10-15